Biomedical subjects

S K Holford

Publications and source records attributed to S K Holford.

5 recordsLinked to original sources

PubMed1986

Observer agreement, chest auscultation, and crackles in asbestos-exposed workers.

Investigators cite observer variability as a problem in using crackles to diagnose asbestosis. We measured agreement on the presence or absence of crackles noted during auscultation of 64 asbestos-exposed workers in order to clarify this question. There was 89 percent agreement between two observers who simultaneously examined subjects breathing from functional residual capacity (FRC). Kappa (kappa), a statistic accounting for chance agreement, was 0.73. Unanimous agreement between four observers who listened to tape recordings of the breath sounds was 81 percent (kappa = 0.69). When the subjects breathed from residual volume (RV) there was 78 percent (kappa = 0.53) and 67 percent (kappa = 0.60) agreement, respectively. Comparing direct to tape-playback auscultation, there was 90 percent (kappa = 0.77) and 84 percent (kappa = 0.58) intraobserver agreement when the subjects breathed from FRC and 90 percent (kappa = 0.79) and 75 percent (kappa = 0.39) when they breathed from RV. We conclude that observer variability is sufficiently low to allow trained observers to monitor asbestos-exposed workers for crackles directly and during tape-playback auscultation.

Adult↗

PubMed1984

Crackles in the early detection of asbestosis.

We studied 386 workers exposed to asbestos to assess the value of chest auscultation by a trained technician in detecting asbestosis as defined by previously reported clinical, physiologic, and roentgenologic criteria. The presence and degree of crackles were assessed at preselected basilar lung sites by a technician whose performance was validated by comparison with computer-generated time-expanded waveforms of tape recordings of lung sounds. Asbestosis was present in only 2.8% of the total population, but it was present in 8.6% of those with over 25 yr or more of employment. The technician correctly identified all the workers in whom the diagnosis was most certain, that is, those with all criteria positive. The overall true positive rate was 55%. The majority (94.8%) of those with no abnormal criteria were correctly classified. Auscultation by an objectively validated technician can be a useful noninvasive method for screening industrial populations exposed to asbestos.

Allied Health Personnel↗

PubMed1983

Discrete lung sounds: crackles (rales) as stress-relaxation quadrupoles.

We modeled discrete emission of sound from lung parenchyma as a point source in an ideal medium. The point source, a quadrupole, represents the stress anomaly in lung parenchyma in the neighborhood of a collapsed airway, and its time course when the airway opens. The dynamics of the airway opening event are characterized by a single time constant. The ideal medium, lung parenchyma, was modeled as a homogeneous linearly elastic lossless nondispersive continuum of infinite extent undergoing infinitesimal strains. Despite its simplicity, this elementary model leads to predictions of crackle waveforms, spectral densities, and spatial intensity distributions which are consistent with observations. In particular, the model predicts changes of waveform shape and polarity with observation position relative to the source, dramatic influences of transduction processes, and successive increases in zero crossing time intervals.

Biomechanical Phenomena↗

PubMed1982

The prevalence and character of crackles (rales) in young women without significant lung disease.

Although some investigators have reported that crackles are present only in persons with lung disease, others say they also occur in normal persons. In order to clarify this difference of opinion, we determined the prevalence of crackles in 56 women without significant lung disease. The subjects ranged from 19 to 33 yr of age (mean, 21.3). They all had a FVC greater than 80% predicted and a FEV1/FVC ratio greater than 75%. None had a history of acute or chronic lung disease. During slow inspirations from residual volume, midinspiratory fine crackles were heard at the anterior bases in 35 of 56 subjects by a physician using an acoustic stethoscope, whereas a bioengineer using an 800 Hertz high pass filtered stethoscope heard crackles in 53 subjects. Crackles during tidal breathing were heard in 2 subjects. It is postulated that the crackles noted after expiration to residual volume are nonpathologic, and occur when basilar airways, which close at the end of a forced expiration, suddenly open during inspiration. Examination of the quality, timing, and anatomic distribution of the crackles in apparently normal subjects suggests that they can often be distinguished from those resulting from diseases such as bronchitis, interstitial fibrosis, and congestive heart failure.

Adult↗

PubMed1977

Visual lung-sound characterization by time-expanded wave-form analysis.

To characterize lung sounds objectively, we examined, by means of time-amplitude plots, selected tape recordings of auscultatory phenomena considered by six observers to be typical of those in a standard classification. Normal lung sounds could not consistently be visually distinguished from adventitious sounds at conventional chart recorder speeds of 100 mm per second or less, but the differentiation was easily achieved when the time scale of the plots was raised to 800 mm per second. When discontinuous sounds (rales, crackles or crepitations) were heard clinically, the time-expanded wave forms showed intermittent "discontinuous" deflections usually less than 10 msec in duration. When continuous sounds (rhonchi or wheezes) were heard, the deflections were usually more than 250 msec. Time-expanded wave form analysis provides reproducible visual displays that allow documentation of the differentiating features of lung sounds and enhances the diagnostic utility of the sounds.

Auscultation↗